The present invention relates to a process for the enrichment and separation of oxides of heavy hydrogen isotopes from acid, aqueous solutions or other aqueous streams in which macrocyclic aminopolyether (APE) and an organic cation exchange agent are used, and in which there is a multi-stage repetition of single stages of enrichment of the heavy hydrogen isotopes on the APE and of single stages of release of the isotopes from the APE in the form of their oxides.
A process according to the above type is known from the German patent publication DE No. 32 02 776 A1 and corresponding U.S. Pat. No. 4,519,996. There, heavy hydrogen isotopes, namely, deuterium and/or tritium, are removed with the use of isotope exchange equilibria from aqueous streams containing them, especially from those streams encountered in the reprocessing of irradiated nuclear fuels and/or breeding materials. In one embodiment of the process disclosed in German DE OS No. 32 02 776 A1 and corresponding U.S. Pat. No. 4,519,996, in a first stage of the process, the acid, aqueous solution or another aqueous stream containing deuterium and/or tritium is first put in contact with a macrocyclic aminopolyether (APE) and, after completely dissolving the APE in aqueous solution or aqueous stream to form a liquid phase, the liquid phase is brought into contact with an organic cation exchange agent in its H.sup.+ form. After a certain amount of time which is needed for the adjustment of the exchange equilibrium, on the cation exchanger, the ion exchange phase, now containing the APE and heavy hydrogen, is separated by filtration from the liquid phase which is now depleted in heavy hydrogen. The solid ion exchange phase then is added to a column and rinsed with an aqueous base, containing heavy hydrogen ions, for example, with an aqueous 30% tetraethylammoniumhydroxide solution, to release the heavy hydrogen from the APE and thereby obtain an eluate which is enriched with heavy hydrogen. This eluate can be subjected to a further exchange in a separate stage to obtain a solution which is further enriched with heavy hydrogen in the elution product.
After the release of the heavy hydrogen from the APE in the first stage, the APE is still on the cation exchange agent. By treating the cation ion exchange agent with an acid, the APE is removed from the cation exchange agent matrix, and then is fed to an anion exchange column. The elution product of this anion exchange column contains the free aminopolyether in aqueous solution, and the free aminopolyether can be recovered by evaporation of the aqueous solution and recycled for reuse. For the removal of the APE from the cation exchange agent, it is also possible to use a lithium chloride solution instead of an acid. The APE is then extracted from the lithium chloride solution with the aid of an organic solvent. The APE recovery then is done by evaporation of the organic solvent, and the APE can then be reused.
The embodiment of the process disclosed in DE-OS No. 32 02 776 A1 and U.S. Pat. No. 4,519,996 which works with APE and cation exchange agents has some aggravating disadvantages which are unacceptable for continuous use, especially the use of additional chemicals needed for the regeneration of the APE and ion exchange columns, and the connected appearance of secondary waste when using the procedure in a nuclear installation (for example, the formation of additional amount of potassium nitrate).